This invention relates to telecommunications systems, and in particular to the supply of electrical power to equipment in a telecommunications network.
In the public switched telephone network (PSTN) it is known to provide power from the exchange, or from an intermediate point such as a street side cabinet, to a remote point such as customer premises equipment or another intermediate point such as a drop-point, using the telephone wires themselves—the traditional twisted wire pair, usually made of copper. In the early development of telephone systems, when mains electricity was still comparatively rare, this allowed provision of service to premises which had no reliable power supply, or a supply which was unreliable, and it is still a useful feature of the PSTN system that communication is possible during a local power failure—in particular so that a call can be made to the electricity suppliers to alert them to the power failure.
Telephony access networks were originally designed to carry low frequency voice traffic, but have since been adapted for high speed digital information, for example using Digital Subscriber Line (DSL) technology. The frequencies used for DSL have greater losses in transmission, and this limits the achievable bitrate, particularly on long lines where the losses are greater. A number of schemes have been used to put access multiplexers at intermediate points such as Digital Subscriber Line Access Multiplexers (DSLAMs) installed in street cabinets closer to the user termination point, to reduce the distance between the customer and the multiplexing point. Such an arrangement allows several customer premises equipments to share the available bandwidth between the street cabinet and the exchange, which is possible as data connections are typically “bursty” (variable in their bandwidth requirements) so that although each customer requires a high bandwidth to be available, it is only required for brief periods. Thus several users can share one high bandwidth connection. However, this approach may not be feasible where customers are geographically dispersed.
It is known to provide a link using a medium other than an electrical conductor to carry a communications connection over part of the route between the exchange and customer premises (herein referred to as a non-electrical link). The non-electrical link may be optical fibre, radio or some other medium. Typically, the necessary transceivers at each end of the non-electrical link require a local power supply. Traditional street cabinets are merely junction points in the distribution network, with no operational or computing power. If a DSLAM, or an electrical-to-optical or electrical-to wireless transceiver is to be installed at such a location, electrical power has to be supplied to the cabinet. However, connection of a mains electricity supply to such locations can be difficult.
The present invention, and the inventions which are the subject of the present applicant's related patent applications filed on the same date as the present application, claiming priority from European applications 12250064.8 and 12250065.5, and entitled, “Delivery of Electrical Power” and “Control of Line Power”, all relate to managing the use of wire telecommunications lines to provide power to remote equipment. It is known for a wired telecommunications system to be used to distribute electrical power to remote points in the system, such as a drop-point. In particular, there have been proposals for electrical power to be supplied from the customer premises end to support one end of a wireless or fibre communications link, for example, to support wireless broadband connectivity over the access network. Examples are described in International Patent specifications WO2009/138710 and WO2009/138711. The power supply operates independently of any call traffic either over the wireless digital channel or “POTS” (analogue telephony) connection.
The present invention relates to the provision of a communications connection comprising a first intermediate connection point, a second intermediate connection point, and a non-conducting communications link between the first intermediate point and the second intermediate point;                the first intermediate connection point being connectable by way of a first conducting link to a telephone network connection point and the second intermediate point being connectable by a plurality of second conducting links to a plurality of remote customer premises installations, at least one of the first and second intermediate points having conversion equipment for converting transmissions between electrical signals carried over its respective conducting link, and a non-electrical signal carried over the non-conducting link        the respective first and second conversion equipments being electrically powered, and having respective power conversion equipment for receiving electrical power delivered over the respective conducting links from the telephone network connection point and the customer premises installations.        
In one embodiment the first intermediate connection point is connectable by way of a first conducting link to a telephone network connection point and the second intermediate point is connectable by a plurality of second conducting links to a plurality of remote customer premises installations suitable to form a communications connection between the telephone network connection point and the customer premises installation
Typically, the conducting links are of the traditional twisted wire-pair type used in conventional “plain old telephony services” (POTS): On the network side, these may have been upgraded, but many connections to customer premises have remained in use for many years, and the extent and range of the telephone network make it likely that many of them will continue in use for many more years to come. Such links are often unsuitable for carrying modern high-bandwidth services over any but very short distances, and so it is often desirable to replace all but the “final drop” with some other mode of communications link. Electromagnetic means such as wireless or optical fibre communications provide a greater bandwidth, over distances not practical for a wired connection. In this specification these are collectively termed “non-conducting”, and in the invention such a non-conducting link is provided between the first and second intermediate points.
Conversion between conducting and non-conducting modes requires an electrical power supply at each of the intermediate points. The invention provides for this power to be delivered over the respective first and second conducting links, from the network connection point and the customer premises respectively.
The first intermediate point may serve several connections, each having its own respective first conducting link. One, several, or all of these connections may be converted to non-conducting mode at the first intermediate point, for forwarding in non-conducting mode to one or more respective second intermediate points. The power delivered from the network connection point can be delivered to the first intermediate point over any one or more of the conducting links, and does not have to be limited to, or even include, conducting links associated with the network connections served by the non-conducting links. Apportionment of the power to be delivered by each of the various first conducting links can be controlled to maintain the overall voltage level on each line within predetermined limits, dependant on the traffic carried on the respective connections.
The second intermediate point serves several connections, each having its own respective second conducting link, and the power to be delivered to the second intermediate connection point can be sourced from any or all of the customer premises locations served by that point. Again power can be apportioned according to the characteristics of each connection, which on the customer side may include significant differences in “final drop” line length or quality, and whether the customer premises equipment is able to deliver power, as well as the traffic volume considerations discussed above. In particular, each link need only draw power if the respective customer is using his communications line. When two or more customers are using their communication lines, the link is powered by the plurality of customers. This is achieved by sensing the usage of the communications line and distributing the amount of power drawn between the users. A more powerful (larger bandwidth capacity) link may be provided if the number of users increases above a threshold level.
The wireless link need not be permanently supported: more particularly it is only required when at least one data session is in progress between a customer premises and the network side of the connection.
The invention therefore powers both ends of the non-conducting link from the respective conducting links connected to the respective intermediate points.
It is desirable that the equipment powered at the second intermediate point (customer end) can be provided with at least a limited service even in the event of power failure at the customer end. In order to achieve this, a conventional twisted pair connection also connects the termination points of the non-conducting link, which can be used in certain circumstances to carry analogue telephony, or a limited digital capacity. A particular circumstance would be in the event of failure to the power supply to one or other end of the non-conducting link.
Limited control and management signals may be carried over this link to instruct the transceivers to switch on and start drawing power in order to initiate a high bandwidth data session. However, since most such sessions are initiated from the customer end, powering up of the second intermediate point can be initiated locally. For the first intermediate point, being connected to the exchange end, it is more convenient to maintain the power connection whether or not any communications sessions are currently in progress.
The invention therefore provides an arrangement in which the exchange and customer each power one end of a non-conducting bridge which is used to bypass the limited capacity available on a conducting connection.